This invention relates to a steering system for a multi-wheeled vehicle, and in particular to a system including means for momentarily isolating the rear wheels from the front wheels for permitting independent steering of the rear wheels relative to the front wheels.
Vehicles, such as movable construction equipment, are typically supported on wheels for movement along the underlying road or other surface. As is well known, the vehicles must be steerable in both forward and backward directions to permit safe and efficient operation.
Multi-purpose equipment is available for use in varied applications including railroad maintenance. When so employed, the wheels of the vehicle straddle the railroad's rails. Generally, such equipment has three independent steering modes of operation, i.e. four-wheel steer, front-wheel steer and crab steer, for steering the vehicle when moving in a forward direction.
In moving in the reverse or backward direction, it is necessary that the rear wheels be independently steerable to prevent the wheels from "climbing" the rails. Since the vehicle generally moves in a forward direction, the control for switching the steering system from one of the forward steering modes of operation to the reverse mode of operation should be readily and easily accessible for actuation by the vehicle's operator. Further, the control should enable the operator to readily return operation of the equipment to the desired forward steering mode.
Further, it is sometimes desirable to independently steer the rear wheels of the machine when moving in a forward direction. If the vehicle is moving along a road in a selected steering mode and the operator recognizes that the rear wheels require independent steering, the present invention enables the operator to (1) segregate the rear wheel steering system from the front wheel steering system (2) independently steer the rear wheels, and (3) automatically return operation of the vehicle to the selected steering mode. As the operator can still independently steer the front wheels while steering the rear wheels, the vehicle's forward travel does not have to be interrupted while the operator is repositioning the rear wheels.